A camper superstructure of the above-mentioned type is already known. It is manufactured to fit the chassis of the motor vehicle as a finished unit which is mounted on the chassis frame and joined with the latter by bolts or the like. But it can also be mounted in a short time, so that the vehicle can be used for other purposes e.g. upon removal of the camper unit.
Such camper superstructures consist of prefabricated steel frames, joined with each other by welding or by screws, which are covered with plywood and on the outside with aluminum plates. The cavities between the steel girders are filled with heat-insulating material. The structures are flanged with each other to make them waterproof. The flanged areas are covered with cover strips.
These constructions are highly stable, but require a large amount of material, considerable assembly work and high cost. Besides, they are heavy, which causes a high energy comsumption for the vehicle carrying the superstructure. A disadvantage is also that the heat insulation is incomplete, since the steel girders of the frame parts are thermally conductive and form low-temperature bridges.
It has therefore been tried to make such superstructures of coated plastic hard foam plates (polyurethane-hard foam) without a frame, so that the weight is considerably reduced, and the assembly simplified. But in this "sandwich" construction, the connection of the outer walls with the roof is highly problematic, due to the low load capacity of the plastic material. In order to provide a base for the application of screws, wood strips are therefore inserted into the edges of the hard foam plates, which permit a firm connection of roof and outer walls by means of screws. But these screw areas must be covered with plate webs for sealing. The necessary flanges on the outer walls and on the edges of the superstructure are covered by means of correspondingly shaped strips.
This design too is time-consuming and costly, and the seals must be made very carefully, otherwise leaks occur.